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Custom Molding

What is Rotational Molding

Rotational Molding is a process used to manufacture hollow, seamless plastic parts. Parts are long lasting, durable, lightweight and resistant to corrosion. A finished part can be constructed using numerous rotationally molded pieces. For example: The SkyShed Pod is a designed product that is rotationally molded in sections to create a top of the line finished product.

Common molded parts include containers, leisure craft, furniture, sporting equipment, agricultural and garden equipment, tanks, toys, medical and industrial equipment, as well as automotive and transportation components. SPI uses rotational molding for the manufacturing of several product lines including: indoor and outdoor playground, livestock waterer, and many custom molding projects.

Our rotational molding can effectively produce small to large, and simple to intricate parts. At SPI, we’ll work with you to determine the requirements of your unique project, ensuring each aspect of your final product reflects those specifications.

Benefits of Rotational Molding

There are many advantages associated with rotational molding:


  • Vibrant beautiful colour availability
  • Custom colours are available
  • Ease of colour changes between production runs
  • Uniform colour throughout the wall thickness
  • Selection of surface textures and finishes
  • Colours are U.V. stabilized

Production Flexibility

  • Flexibility of small to large production runs as required, allowing for flexibility of your inventory management
  • Standardized packaging, reducing your inventory management and costs
  • Ability to alter wall thickness as required by adjusting part charge weight
  • Colour changes
  • Addition of inserts

Product – Complexity and Design

  • Design flexibility to meet specifications
  • One piece, seamless shapes can be created. From simple to complex shapes, with strong corners, walls and structures that are virtually stress-free
  • Uniform wall thickness with no thinning of extremities
  • Flexibility of single wall parts or hollow double wall parts
  • Double wall construction capabilities allow a product to be designed with load bearing properties and structural strength, without adding a great deal of weight
  • Double wall construction also allows for differences in appearance on the interior and exterior walls; this flexibility allows the double wall cavity to be filled with other materials, eg. insulating materials
  • Molded in graphics and logos for identification
  • Addition of molded-in inserts

Tooling Costs

  • Relatively low tooling costs vs. injection or blow-molding processes
  • Quick tooling fabrication
  • Long tooling lifespan
  • Flexibility of multi-cavity tooling for high production needs
  • Selection of tool fabrication materials

SPI Custom Molding

Molding plastic isn’t enough; SPI offers the talents and strength of a full service company ready to meet your challenges and requirements. There are many products both created and used each day throughout the world that can be adapted and/or enhanced by rotational molding techniques. SPI provides customer service second-to-none!

Why SPI for Your Custom Rotational Molding Project?

Product Design

From Concept to Completion

SPI provides clients with excellent Technical Design Support. We pride ourselves in taking full advantage of technological advances to satisfy and fulfill your unique requirements.

Our product development team of qualified professionals will take you on a journey from “Concept to Completion”, keeping you involved, informed, and on board throughout the entire process. Simply put, SPI shares your goals to create quality products!


We use Computer Aided Designs (CAD) to provide three dimensional (3D) perspectives to both customers and mold makers.
CAD allows us to provide colour renderings or line drawings, producing life-like qualities to your concept.

Product Development

At SPI, our future products are the result of innovative thinking today. Product development is non-stop at SPI. Innovation and diversification are our keys to success. These talents are here to help in creating your success, and our product development team provides new visions which become product realities.

Have something in mind? Ask us about your custom rotational molding project!

Tooling and Prototypes


Tooling and prototypes are key to your custom design project. SPI provides you options from start to finish.

  • cost-effective tooling options
  • innovative design
  • mold maintenance options
  • tooling, prototypes and production parts delivered timely


  • bushing, inserts, core pins
  • cast aluminum
  • CNC tooling
  • fabricated aluminum
  • molded-in inserts
  • multiple cavities
  • textured surfaces


Secondary Processes

Once your part has been rotationally molded, there are a large variety of Secondary Operations that occur. For example, parting lines can be trimmed and to achieve shine, your part can be flame polished. Rotational molded parts can be drilled, milled, sawed, or spin welded, and cooling jigs or fixtures may be used.

SPI also offers pre-assembly of custom sized orders. The below photograph demonstrates a custom order with pre-assembly of a Starglide slide.

Great slide, great fun!


Quality assurance is critical in ensuring secondary processes are carried out and completed with the highest level of expertise and precision.

Our secondary processes are completed in-house at SPI, for efficient service that is equally cost-effective for our clients.

Available Secondary Processes


  • Assembly
  • Bar coding availability
  • CNC Machining
  • Custom Packaging
  • Drilling
  • Flame Polishing
  • Just-in-Time Delivery System
  • Mold Maintenance
  • Molded in Graphics
  • Molded in Threaded Inserts
  • Polyurethane Foam Insulation
  • Welding